I have a Mirage 550 that the wife bought me, that her father built, he's been in the hobby for year. He did a good job with the build and everthing looks ok, the trouble I'm having is the plane is pulling left and the gent I had take it up on it's maiden had to put all the right trim the radio had, and could still use more. The only thing I found was the left wing tip was heavy buy about 3.2 gram, ( the weight of a penny ), would this be enough to cause the plane to pull hard left like this, or need I look else where??????????

Actually that's about the weight of three one dollar bills and is insignificant. Trim the servo and fly it.

Check for warped wings -either one or both (you want some washout in both)! Check for not enough right thrust in motor or even some left thrust. Check alignment of tail surfaces - both fin and stab. either one could cause a turn if not square to one another and to the main wing.
Walt

PS if you do have to build the trim in, then adjust the appropriate surface (rudder?), not the servo.
WT

Wouldn't you want to mechanically trim first before electronically trimming? Perhaps I misstated it by saying "trim the servo first". Guess I am lucky computers dot the "i" and crosses the "T". I meant to say mechanically trim it first. By the way "left wing tip was heavy buy about 3.2 gram" should have been "left wing tip was heavy by 3.2 grams.

I forgot to mention doing a lateral balance as well.

and yes you should always trim mechanically first and only use servo trim for changing flight conditions (but then I'm an old fart - I started r/c long before computer radios). All my aircraft have the same basic control set-ups so that if I screw up and select the wrong model I can still fly - it may be way the h- out of trim, but I can fly it!
Walt